Biology data test

Question 1

P values and error bars

Answer 1

p <0.05 is significantly different).
p <0.01 is highly significantly different).
p>0.05 is more likely due to chance
error bar overlap is not significantly different

Question 2

Menhinick Index for Species Richness

Answer 2

To account for sample size sometimes Species richness is also calculated using the Menhinick Index where the number of species (s) is divided by the square root of the number of individuals in the sample (N).

Menhinick Index for Species Richness (D)
=s/√N

Question 3

Species diversity and species richness

Answer 3

Species diversity is a measurement of species richness and species evenness. Species richness is just the number of species.

Question 4

Unpaired/ paired
One-tail/two-tail t-tests

Answer 4

Unpaired: different data (e.g. different sites)
One tail: predicted increase
Two tail: predicted change

Question 5

Simpson’s Diversity Index (SDI)

Answer 5

: N = total number of organisms of all species n = number of organisms of one species)
1-(sum of n(n -1)/(N(N-1)
When comparing species diversity from different areas / ecosystems, the closer the SDI number is to 1, the higher the diversity. The SDI also provides the probability that any two individuals chosen at random and independently from the community will be found to belong to different groups (species).

Question 6

Symbiosis

Answer 6

Mutualism: association between two or more species where each species benefits.
Commensalism: association between two species in which one species benefits and the other derives neither benefit nor harm. (eg.
Parasitism: an association between species, where one species, (the parasite living on or in another organism) benefits while the other (the host) is harmed. (eg ticks, tapeworms. It also occurs in rainforests. The strangler fig grows competes for water, nutrients and sunlight with a host tree. Typically, the host tree dies, and eventually decomposes, leaving the fig tree standing independently)
Amensalism: an association between two different species in which one is inhibited or destroyed and the other is unaffected (eg. occurs in Australian rainforests. Tall trees reduce the available sunshine at ground level, and numerous plants cannot find adequate light in the shade).

Question 7

Species Interactions

Answer 7

• Predation
• Competition
• Symbiosis (Mutualism, Commensalism, Parasitism)
• Disease: Temporal and spatial factors will affect how these pathogens or parasites can be spread. Organisms living in close proximity to each other to each other will allow the spread to occur faster. Seasonal variations can also affect the ease at which a pathogen or parasite can be spread.

Question 8

Abiotic Factors

Answer 8

• Climate: tropics vs poles, or how the microclimate changes as you move from the tide line up the beach
• Substrate: eg at the beach consider sand, rock, wood or soil substrate
• Size/depth of area: comparing the size of different rainforests in two completely different countries, the depth of any aquatic environment, from rock pools to trenches.
• Vary along spatial gradients to produce environmental gradients
• Each species in an environment has a range of abiotic conditions most suitable for its survival and reproduction… Therefore, these gradients are important determinants in patterns of species distribution.

Question 9

Biotic factors

Answer 9

(i) Intraspecific relationships (same species)
* May increase surviving an attack by a predator
* Compete for limited resources such as food, shelter, water, a mate etc…
(ii) Interspecific relationships (between different species)
* Predation: predator kills prey and eats it
* Competition for limited resources
* Symbiosis: two or more species living closely together for a long time. At least one organism benefits

Question 10

Surveying techniques

Answer 10

Transects, quadrats, capture-mark-release-recapture

Question 11

Transects

Answer 11

Line transects:
Strengths: Line transects are good to use as they can be quick and also can be used to collect abiotic data and to visualise change in the distribution of species along gradients.
* Limitations: Line transects do not provide good data on species density (or estimating moving animal population)

Belt transects:
* Strengths: Belt transects allow the collection of abiotic data, species distribution and species density / abundance to be determined across a range of strata along a gradient.
* Limitations: Belt transects are very time consuming and do not provide good data on species density (or estimating moving animal population)

Question 12

Quadrats

Answer 12

square areas. Strengths: good for estimating the population size / density of stationary organisms (plants, fungi, sedentary animals). Limitations: can be time consuming, can be discrepancies in method used to count organisms (eg. counts vs percentage cover), if randomly placed may not sample all strata well and quadrats are not good for counting moving animals. Smaller quadrats should be used for smaller organisms.

Question 13

capture-mark-release-recapture

Answer 13

is good for estimating population size.(Use Lincoln Index) Strengths: useful for use with moving animals (in combination with Lincoln index). Limitations: Takes a long period of time to collect data.

Question 14

Sampling methods

Answer 14

systematic or random sampling
* Systematic sampling is where quadrats placed / data collected at regular intervals along a gradient / transect line.
* Random sampling involves using a numbers generator to randomly position quadrats. The quadrats within each stratum should be randomly placed. (Note: If a stratum represents 10% of the total area studied then 10% of the total quadrats should be used there)

Question 15

Minimising bias and error

Answer 15

• ensure an appropriate number of samples / quadrats from each stratum,
• ensure samples / quadrats are taken / used randomly (random sampling) eg via a random numbers generator
• ensure counting criteria are identified (eg. via counting individuals or estimating % cover for plants), and data for multiple quadrats in each stratum can be averaged.
• ensure equipment for measuring abiotic factors is calibrated (eg. pH probes) and any measurement error associated with equipment use is identified.

Question 16

Limiting factors

Answer 16

Limiting factors are resources that a population requires but which if present in small quantities, negatively impacts on population growth (creates unfavourable conditions for the population). Limiting Factors can be density dependent or density independent.

Question 17

Density-independent factors

Answer 17

Affect the population size regardless of the density / size of the population. Two major categories of these:
i) regular abiotic conditions eg. water availability, temperature, light levels, salinity that impact on survival.
ii) irregular disturbances eg. flood, fire, drought.

Question 18

Density-dependent factors

Answer 18

Affects on population size are determined by the size of the population (effects increase as population increases)
Major examples include: competition for resources (eg interspecific & intraspecific competition), predation, disease, overcrowding effects.

Question 19

Environmental resistance

Answer 19

Environmental resistance is the sum total of all the environmental limiting factors. As a result of this environmental resistance, the population will be restricted to the carrying capacity of the environment in which it lives. Each population has a maximum size that can be sustained over a long period (carrying capacity) and this is determined by the limiting factors.
As a result of environmental resistance (particularly caused by density-dependent factors), the growth of the population slows, and possibly ceases altogether.

Question 20

Population change

Answer 20

N = (B + I) - (D + E)
* N is the change in population.
* B is the number of births.
* I is the number of immigrants, or people who have moved into the area.
* D is the number of deaths.
* E is the number of emigrants, or the number of people who have moved out of the area.

Question 21

Lincoln index

Answer 21

M = number of individuals caught, marked and released initially
n = number of individuals caught on the second same
m = number recaptured that were marked

N= (Mxn)/m

Question 22

r strategists:

Answer 22

are species that often live in unstable environments and can produce a large number of offspring rapidly. They are often small in size, short lived and exhibit little parental care, reproduce rapidly and exhibit exponential growth curves. (eg. bacteria, insects, rodents, weeds, grasses).

Question 23

k strategists:

Answer 23

are species that often live in stable environments and produce few offspring. They are often large in size, long lived, exhibit extensive parental care and are often very competitive for resources and often exhibit logistic growth curves. (eg. elephants, primates)

Question 24

J shaped population curves

Answer 24

J shaped population curves depict an exponential growth mode and are typical of opportunistic density independent species such as insects or weeds. These organisms typically are short lived, have short generation times and give rise to a large number of offspring rapidly (see r strategists info below) and will continue to exhibit a population explosion while resources are plentiful / unlimited (growth may be stopped suddenly by a limiting factor causing a population crash).

Question 25

S shaped population curves

Answer 25

S shaped population curves depict a logistic growth mode and are typical of density dependent species. These organisms typically are relatively long lived, have long generation times and give rise to only a few offspring at a time (see k strategists below). Population growth increases slowly, then exponentially until it levels off as environmental resistance (density- dependant factors) limits growth and carrying capacity (a stable population level) is reached.

Question 26

Carrying capacity

Answer 26

Note that Carrying Capacity is dynamic. The carrying capacity for a population is not always constant, it can vary over time due to changing levels of limiting factors / environmental resistance. (eg. seasonal changes in climate or fluctuating levels of predators or competitors).
NOTE: If a resource (limiting factor) suddenly becomes scarce (eg. due to temperature drop, fire, drought, overhunting) then the population may suddenly exceed the carrying capacity of the environment causing a population crash…. Ultimately, the carrying capacity of an environment is tied to the availability of the scarcest resource.

Question 27

Primary succession

Answer 27

Primary succession occurs over broad time scales where bare areas are colonised for the first time, such as on lava flows, new sand dunes, new coral reefs and land exposed by retreating glaciers.

Question 28

Secondary succession

Answer 28

Secondary succession occurs over short time scales in previously vegetated areas where there has been a disturbance that resets the community to an earlier stage of succession. (Note: disturbances can include natural disasters such as wildfires or floods, human impacts or smaller events such as a tree falling in a rainforest).